When is the actual 1st day of a period?

Diana • Engaged 🖤44 Y.Old Vamp ⚰ Mother of 2 vamps🖤 Miscarried 2👼 5/18 @12wks & 3/19 @24wks 💔 Hoping for a healthy miracle one more time. 🙏🐣🍼🤱

So I am confused, Do you start to count the period days when you start spotting or when you actually have a full blood flow?? Because I've always counted 5 days total for me, that's 2 days of spotting @ the beginning then 2-3 days of full flow. And I read somewhere that it's when the full flow cones in when it starts to count, my hubbie and I are currently TTC and if this is correct then no wonder we have not hit jack pot 😕